I have a serious problem to log in on my second site of a WP network installation. This relates to the theme site log in page, not that of WP. I would like to offer the customers just one page to register and log in, so I just removed the registration button from the sub menu. This looks like this: http://epicase.de/mein-konto/

I did this also, because the registration page forwarded always to the fist site.

What can I do process the whole registration process over the log in page of the them?